Image exposure and development method and apparatus

ABSTRACT

The image exposure and development apparatus provides for exposure of a sensitive medium which is developable by the deposition of atoms thereon, such as a sensitized nucleation material and development thereof by the deposition of metal from metal vapor. Following exposure, the exposed medium is continuously fed to and wrapped around a major portion of the circumference of spaced discs. Atoms from a vapor source between the discs impinge upon the medium and the latent image thereon is developed by selective acquisition of the metal onto the surface. The surface characteristics of the medium and discs are such that little metal is deposited upon the discs.

United States Patent Kaspaul 1 51 3,664,249 1 51 May 23, 1972 [54] IMAGE EXPOSURE AND DEVELOPMENT METHOD AND APPARATUS [72] Inventor: Alfred F. Kaspaul, Malibu, Calif.

[73] Assignee: Hughes Aircraft Company, Culver City,

Calif.

22 Filed: Feb. 17, 1971 211 Appl. 190.; 115,943

Related US. Application um [62] Division of Ser. No. 789,997, Jan. 9, 1969, Pat. No.

[52] US. Cl. ..95/13, 95/89 R, 355/27 [51] Int. Cl. ..G03b 17/50 [58] Field ofsearch ..95/13, 89 R, 89 G, 93,94 G;

[56] References Cited UNITED STATES PATENTS 2,948,261 8/1960 McGraw ..1 18/49 3,565,523 2/1971 Davis et a1. ..95/89 G 3,585,917 6/1971 Griflith ..355/27 X Primary Examiner-Samuel S. Matthews Assistant Examiner-Fred L. Braun Attorney-W. H. MacAllister, Jr. and Allen A. Dicke, Jr.

[57] ABSTRACT The image exposure and development apparatus provides for exposure of a sensitive medium which is developable by the deposition of atoms thereon, such as a sensitized nucleation material and development thereof by the deposition of metal from metal vapor. Following exposure, the exposed medium is continuously fed to and wrapped around a major portion of the circumference of spaced discs. Atoms from a vapor source between'the discs impinge upon the medium and the latent image thereon is developed by selective acquisition of the metal onto the surface. The surface characteristics of the medium and discs are such that little metal is deposited upon the discs.

9Clalms,1lDrawlngFlgures Patented May 23, 1972 3,664,249

7 Sheets-Sheet 1 Alfred F. Kospoul,

INVENTOR.

ALLEN A. DICKE, Jr.,

AGENT.

Patented May 23,1972 3,664,249

7 Sheets-Sheet 2 Alfred F. Kospoul,

INVENTOR ALLEN A. DICKE, Jr,

AGENT.

Patented May 23, 1972 3,664,249

7 Sheets-Sheet I) Fig. 4c.

Time

swow aoopns ;o J9qUJnN Alfred F. Kospoul,

INVENTOR.

ALLEN A. DICKE, Jr.,

AGENT.

Patented May23, 1972 7 Sheets-Sheet 4.

swow aaopns ;o Jaqwn Alfred F Kospoul,

INVENTOR.

ALLEN A. DICKE, Jr.,

AGENT Patented May 23, 1972 7 Sheets-Sheet b Higher flux rate Intermediate flux rate Time 1 Uniform Metal Flux Lower flux rate swow aaopns o .ueqwn Aifred F. Kaspoul,

INVENTOR.

Fig. 4c.

ALLEN A. DICKE, Jr,

AGENT.

' Patented May 23,1972 3,664,249

'7 Sheets-Sheet G Fig. 6. PRIOR ART Alfred F. Kospoul,

INVENTOR.

ALLEN A. D|CKE,Jr.,

AGENT Alfred P Kaspoul, INVENTOR ALLEN A. DICKE, Jr.,

AGENT.

IMAGE EXPOSURE AND DEVELOPMENT METHOD AND APPARATUS CROSS REFERENCE BACKGROUND This invention is directed to a method and apparatus for exposing and developing a photosensitive medium, which medium has a latent image thereon whichis developed into a visi ble image by means of the selective deposition of metal atoms thereon from a vapor. t I

A number of prior art processes for the recording of information and subsequent formation of visible images employ the selective deposition of various materials onto latent images. An example of this is found in A. F. Kaspaul et al., U.S. Pat. No. 3,235,398, granted Feb. 15, 1966. A number of other inventions are directed to the same general type of process, These processes employ the selective deposition of metal atoms to create the visible image. A. F. Kaspaul et al., U.S. Pat. No. 3,140,143, granted July 7, 1964, describes the use of a metal chosen from Group 11-3 of the periodic system, as a metal which can be employed with the particular substrate disclosed therein. Selective deposition can be accomplished on suitable substrates by the employment of a variety of other materials as they are discharged from a boiler or any other suitable source. Additionally, a metal chosen from Group I-B or magnesium is suitable and can be employed'in the same way. In other cases, the developer material is provided by the dissociation of a metal-containing compound, such as silane. Furthermore, cadmium sulfide, lead sulfide, bismuth trioxide may be deposited in imagewise fashion to produce active elements for microcircuitry applications, as described in A. F. and E. E. Kaspaul U.S. Pat. No. 3,333,984, granted Aug. 1, 1967. Additionally, while the three cited prior patents describe the selective deposition of metals, metal chalcogenides, etc., for image production, such deposition can be employed for other purposes, such as providing a conductive path, or the like.

The prior art teachings are directed to batch-type processing, as well as toward continuous applications. However, they have not resulted in efficient employmentof the vaporized materials at high processing speeds. Accordingly, in the prior art applications, a sizeable fraction of the developer" is deposited within the development chamber rather than onto the substrate. Thus, in continuous usage, material is wasted and frequent cleaning is necessary.

SUMMARY In order to aid in the understanding of this invention, it can be stated in essentially summary form that it is directed to an image exposure and development method and apparatus which includes exposure of a nucleation-sensitive material to create a latent image thereon, followed by continuously feed ing the medium to a development chamber which is defined by first and second circular closure plates which define the ends of the development chamber and wrapping the medium substantially around the closure plates to form the radial confines of the chamber. A metal vapor source within the chamber produces vapor which selectively deposits upon the exposed images on the medium. It is a further object of this invention to provide an image exposure and development method and apparatus wherein a portion of the chamber wall is formed by other than the medium and is at such conditions, and the developing vapor flux is adjusted to such a rate that stable deposition does not take place on any of the walls of the chamber except the wall formed by the medium. It is still another object of this invention to provide an image exposure and development method and apparatus which is formed of first and second spaced discs and the medium embraces a large portion of the circumference of the discs to define the image exposure and development method and apparatus therein. It is still another object to provide a structure wherein medium can be continuously exposed and developed by passing it first through an exposure zone and thence circumferentially around an image development station. It is a further object to provide an exposure and development method and apparatus wherein continuous development is accomplished at nearly percent efficiency. Other objects and advantages of this invention will become apparent from a study-of the following portion of the specification, the claims, and the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view of a recording and playback console employing the preferred embodiment of the image exposure and development method and apparatus of this invention.

FIG. 2 is an enlarged partial section taken generally along the line 2-2 of FIG. 1.

FIG. 3 is a partial section taken generally along the line 3- 3 of FIG. 2.

FIG. 4, 4b and 4c are graphs showing various conditions under which selective deposition of atoms and molecules will occur.

FIG. 5 is a schematic view of the development chamber of this invention showing development vapor paths.

FIG. 6 is a schematic view of a prior art development chamber showing development vapor paths.

FIG. 7 is a schematic view of the development chamber of this invention showing an optical wiper therein.

FIG. 8 is a section on the line 88 of FIG. 7.

FIG. 9 is a schematic view of another embodiment of th development chamber of this invention.

A recording and playback console 10 incorporates the,

development chamber 12 of this invention. Console 10 includes housing spaces 14 and 16 for electronics. It is electrically connected and arranged to receive an electronically defined image which can be visually displayed on the face of cathode ray tube 18. In other words, the console receives images and sound in the form of electronic signals resulting from various sources commonly employed in conventional television practice. Thepurpose of the. console is to receive, record, and to play back these signals in a desired line frequency.

' An electron source 20 produces a modulated beam 22 in accordance with the input signals. Beam 22 is focused and deflected by any conventional electrostatic or electromagnetic means, such as focusing and deflection means 24. However, rather than producing orthogonal scan, only lateral scan, corresponding to thehorizontal scan on the image, is produced by the deflection means. Housing 26 encloses the beam, and is pumped to a suitable low pressure at the pump connections indicated for satisfactory beam performance. Draft tube 27 permits beam passage.

As is seen in FIG. 2, tape deck 28 includes a supply of recording tape on reel 30. The tape 32 passes around exit guide roll 34 through slot 36 into a very narrow gap of chamber 38. Capstan 40 rotates simultaneously with capstan 66 within chamber 38, wrapping the tape 32 around its cirspaces in chamber 38 are sufficient to maintain the desired pressures for each area. v

Differential pumping of the recording/readout chambers and the respective gun areas is preferably utilized to minimize the size requirements of the vacuum equipment. FIG. 2 shows an arrangement whereby the gun areas may be held at 5 Torr with a 2 inch diffusion pump by connection to port 39, whereas the recording/readout chambers are maintained at 10 Torr with a 3 inch booster pump by connection to port 41. Development chamber 44 and tape reel chambers of the tape deck 28 operate at E 10 and 10' Torr, respectively, by use of forepumps connected to ports 43 and 45.

From chamber 38, the media 32 passes into the stationary development chamber 44 in which the rotating development chamber 12 is located. As seen in FIG. 3, chamber 44 is closed by transparent cover 46 so that the progress of development can be observed. Bearing post 48 is centrally mounted in recess 44 and hub 50 is rotatably mounted thereon. Circular discs 52 and 54 are mounted upon hub 50 so as to rotate therewith. Preferably, upper disc 54 is conveniently removable from the hub and is transparent for visibility purposes. Tape 32 passes around discs 52 and 54, so that the edges of the medium are engaged thereby, and the discs together with the hub, are-rotated as the medium passes through the stationary development chamber 44. Tape 32 engages around a substantial part of the circumference of the discs, as shown in FIG. 2, to define the rotating development chamber 12 enclosed by the medium and the discs.

Source 56 is the source of atoms and/or molecules for the development of the latent images contained within the medium 32. Source 56 is conveniently a heated coil or mesh which is connected by leads 58 to the secondary of transformer 60. Energization of leads 62 to the primary of transformer 60 causes high current flow through the coil which forms source 56, thereby heating it to the proper temperature. When the coil or mesh is plated with the metal to be vaporized, such as zinc or cadmium, 10 watts is sufficient to develop a 35 mm tape at 36 inches/second, and one coil or mesh can have sufficient material to develop more than several thousand feed of tape. of course, other vapor sources may be employed, e.g., a small boiler could be used to supply the required vapor for many tape reels. Source 56 is preferably positioned so that it is spaced equal distance from all points of the tape as the tape is wrapped around the discs to form the development chamber.

The developer source may be of any type and shape and will successfully operate as long as it is centrally located. Of course an eccentric positioning is possible if one adjusts the efflux pattern accordingly.

After leaving stationary development chamber 44, the now developed tape is transported to chamber 64 where it engages around capstan 66. After leaving capstan 66, tape 32 passes through slot 68 and around guide roll 70 to be wound on tape reel 72. If reading of the image is required immediately following recording and development it may be accomplished with the read out gun 74 scanning across the tape on capstan 66. Electron gun 74 in housing 76 directs an electron beam 78 onto the image-carrying medium. Focus and deflection means 80 scans the electron beam laterally across the tape as it moves past opening 82. As a result of electron impingement, photons are emitted in accordance with the image content of the medium. These photons are focused by mirror 84 onto photomultiplier 86. The image is thus returned to an electronic signal and can be rebroadcast in a different line frequency and/or cathode ray tube 88. Housing 76 is suitable evacuated for proper electron beam conditions, and the narrow spaces around the medium in chamber 64 permit the maintenance of a proper vacuum with minimal pumping equipment.

The usefulness of this invention may best be understood by exposing a given surface to an incident flux of atoms and/or molecules from a molecular oven or other vapor source. Atoms and/or molecules will condense upon the surface, at first moving about it in random fashion. They are eventually captured by active sites to form a stable deposit, or reevaporated from the surface after a certain time has elapsed. At low incident rates, a certain number of atoms will be found upon the surface at any given time so that the equilibrium concentration is reached as soon as the re-evaporation rate equals the incident flux. At equilibrium,

"2 m ani xp rind/R or m =Incident flux, [atoms cm sec" n, Re emitted atoms, [atoms cm sec 1 N,,,, Number of surface adsorbed atoms, [atoms cm' A Frequency constant -10 for most metals (b =Estimated heat of adsorption, [Kcal mole l R Gas constant [1.987 cal deg mole T= Temperature in degrees Kelvin [K] Using zinc for the incident atoms and a glass surface held at 300 K. as the receptor,

log

Using this value, surface concentrations of 10 or 10" atoms/cm" are obtained with incident rates of 10" or 10' atoms/cm coverages of 0 10' (0= N /N N,,, number of possible surface sites in an orderly lattice) no stable twins or even triplets will be produced which have a much longer lifetime than single atoms, thus all atoms will eventually leave the sur-. face, especially upon cessation of the incident flux. In FIG. 4a, curves and 92 indicate this for the two concentrations of 10 and 10 atomslcm respectively. Hence the two glass discs of the development chamber should be free of zinc deposits as long as the surface coverage is kept below 10", and spurious nucleation centers are avoided. FIG. 7 shows a simple solution for the prevention of random nucleation centers in the rotating development chamber.

As previously indicated, the recording tape containing the latent images forms a substantial portion of the development chamber and is therefore exposed to the incident flux of zinc atoms as long as it surrounds the two glass discs and the developer source. During this time interval, atoms and/or molecules will condense and re-evaporate from its surface, which has, with the exception of the latent images, quite similar surface properties as those of the glass discs. Hence no condensation occurs upon the background of the medium.

However, electrons previously impinged upon the medium have created latent images characterized by areas of much greater heat of adsorption for zinc. At an incident flux of about 10 atoms/cm sec., these invisible images develop into visible images, in less than one second, if one assumes that 4 is about 12 K cal/mole for an average portion of the latent image, thus The corresponding surface concentration amounts to nearly 10'' atoms/cm (0= 10) which is much too large to maintain equilibrium condition, hence rapid formation of twins, triplets and stable cluster occurs and continuous film growth is only a matter of time.

Because the previous electron beam incidence upon the tape has modulated the number of nucleation sites, their effective energy and distribution, 4), varies with the information content and one obtains a time dependence of the onset of permanent condensation. This is illustrated in FIG. 4b by curves 94 and 96, assuming a constant incident rate. Curve 94 represents a large exposure to electrons, curve 96 a smaller amount of irradiation, and curve 92 the unexposed background of the tape. The critical surface concentration of about 10 atoms/cm was found experimentally; at this point the re-evaporation rate drops rapidly to zero and every incoming atom must be captured. By carefully controlling the zinc flux and the development speed, all zinc atoms are eventually sec. It may be assumed that up to surface deposited upon the recording tape without any loss of material to adjacent areas. Furthermore, by the very nature of the rotating development chamber, any rise of the incident rate does not precipitate the deposition of zinc on unwanted areas, because the process is self-regulating. This is best explained by FIG. 40.

As shown, the tape enters the rotating development chamber on the left and is immediately exposed to a uniform zinc flux. Depending upon the image content it will take a certain time for even the most energetic centers to take full control over the deposition process, faithfully reproducing the desired information.

For all practical purposes, the time interval, from the first exposure of the tape to the zinc vapor to the onset of barely visible images, ranges from about 0.25 to 0.75 of the total time spent in the development chamber.

Normally the onset of visible condensation is chosen to be at about midpoint in the development chamber by adjusting the incident rate accordingly, hence arise or fall of the number of incident atoms due to various demands of the tape will only shift this point either forward or to the rear without affecting anything else except the final optical density of the images. Curves 90 show the background at the several flux rates while the upper curves show the image deposition at the several flux rates. If unexposed tapes are fed into a development chamber while maintaining a steady efflux from the developer source, the number of available zinc atoms must increase within the volume of the chamber resulting in an excessive incident rate. With the rare exception of the rotating chamber configuration, auto nucleation proceeds. indiscriminately in the system and suddenly zinc atomswill condense everywhere. At excessive incident rates, the rotating chamber seldom becomes coated and the tape will always pick up the zinc even though it has not been exposed to electrons. This is made possible by the most favorable arrangement whereby the tape circles the developer source.

FIGS. 5 and 6 show two extremes, in each case utilizing a filament type zinc source. The FIG. 6 is typical for prior art arrangements and large incident rates are required to produce visible images in the shortest possible time. About 80 percent of the atoms may be lost, at TV-recording rates, whereas by using the rotating development chamber, all re-evaporating atoms are collected, eventually, by other portions of the tape. Of course, a modified development system may be constructed whereby a uniform zinc flux is established over a length of tape. However, this is not a simple approach and requires not only a large area source, as is shown in FIG. 9, but also a sizable backup surface. Since this zinc reflector is not renewed it may become coated in time, and adsorbs all the zinc available. In comparison, the dead area" in the rotating chamber of this invention is quite small and the developer flux incident upon it is far below critical. Furthermore, the two rotating glass disks as well as the hub may be fitted with a stationary wiper or protection means as shown in FIGS. 7 and 8.

This felt-type rectangular wiper block 98 may be soaked in a suitable organic liquid of low free surface energy, thus providing continuous protection for the wiped surface from zinc deposition.

The kind of recording medium is not critical. As a matter of fact, anything that has a controlled variation of the surface free energy upon it may be developed in this manner. The preferred media for electron beam recording/readout in nearreal-time comprise mainly of photoconductive and photoemissive pigments combined with a nucleation inducing compound in a suitable binder. Decomposable compounds yielding nucleation centers of desired configurations upon electron, photon or ion bombardment may also be utilized.

This invention having been described in its preferred embodiment, and an alternative embodiment also described, it is clear that it is susceptible to numerous modifications and embodiments within the ability of those skilled in the art and claims.

WHAT IS CLAIMED IS:

1. An image exposure and development apparatus for the development of media which are developable by the deposition of atoms thereon, said apparatus comprising:

media exposure means for exposing the media to form a latent image thereon; and

a development chamber for receiving exposed media, said development chamber comprising first and second closure plates defining the ends of said development chamber, a source of metal atoms within said development chamber, the media to be developed engaging both said first and second closure plates so as to form the sides of said development chamber to substantially enclose said development chamber, the media being unobstructed for the deposition of metal atoms thereon.

2. The apparatus of claim 1 wherein the image exposure and development apparatus forms a portion of a media-handling system said media-handling system including supply means to supply media to said exposure means and to transport exposed media to said development chamber, and takeup means to remove media from said development chamber.

3. The apparatus of claim 2 wherein said media-handling system includes image-reading means between said development chamber and said media takeup means so that said image-reading means reads the image on the media after development of the media and before the media reaches the takeup means.

4. An image exposure and development apparatus for exposing a sensitive material on an indefinite length of moving web to form a latent image and subsequently develop the latent image to a visible image comprising:

exposure means positioned with respect to the moving web to expose the sensitive material to form a latent image thereon and development means to which the moving web is fed subsequent to the exposure means, said development means comprising:

a pair of axially-aligned, rotatable discs:

means to feed said web in a path to peripherally engage said discs to form a substantially closed chamber with theimage area on the web facing inwardly, the moving web rotating said disc;

a source of vaporized developer material disposed within said chamber to deposit developer material on the web to develop the latent image and form a visible image.

5. The apparatus of claim 4 wherein said discs and web substantially enclose said development chamber so that the metal atoms are unimpeded between said source of metal atoms and the sensitive material and have access to the entire surface of the sensitive material on the web which forms the sides of said development chamber.

6. The image exposure and development apparatus of claim 5 further including protection means for protecting a zone from said source of metal atoms so that, as said rotatable discs rotate past said zone, the portion of said discs facing said zone are protected from deposition of metal atoms.

7. The image exposure and development apparatus of claim 4 wherein said discs'have a concentration of developer atoms on their surfaces below l0 atoms/cm? 8. The image exposure and development apparatus of claim 7 wherein said web is fed from said exposure means and is positioned around said rotatable discs and carries a latent image thereon, the latent image receiving a surface concentration of atoms of developer material in excess of l0 atoms/cm? 9. The image exposure and development apparatus of claim 8 wherein a wiper means is positioned against said discs so that metal atoms deposited upon said discs are removed by said wiper means as said discs rotate. 

1. An image exposure and development apparatus for the development of media which are developable by the deposition of atoms thereon, said apparatus comprising: media exposure means for exposing the media to form a latent image thereon; and a development chamber for receiving exposed media, said development chamber comprising first and second closure plates defining the ends of said development chamber, a source of metal atoms within said development chamber, the media to be developed engaging both said first and second closure plates so as to form the sides of said development chamber to substantially enclose said development chamber, the media being unobstructed for the deposition of metal atoms thereon.
 2. The apparatus of claim 1 wherein the image exposure and development apparatus forms a portion of a media-handling system said media-handling system including supply means to supply media to said exposure means and to transport exposed media to said development chamber, and takeup means to remove media from said development chamber.
 3. The apparatus of claim 2 wherein said media-handling system includes image-reading means between said development chamber and said media takeup means so that said image-reading means reads the image on the media after development of the media and before the media reaches the takeup means.
 4. An image exposure and development apparatus for exposing a sensitive material on an indefinite length of moving web to form a latent image and subsequently develop the latent image to a visible image comprising: exposure means positioned with respect to the moving web to expose the sensitive material to form a latent image thereon and development means to which the moving web is fed subsequent to the exposure mEans, said development means comprising: a pair of axially-aligned, rotatable discs: means to feed said web in a path to peripherally engage said discs to form a substantially closed chamber with the image area on the web facing inwardly, the moving web rotating said disc; a source of vaporized developer material disposed within said chamber to deposit developer material on the web to develop the latent image and form a visible image.
 5. The apparatus of claim 4 wherein said discs and web substantially enclose said development chamber so that the metal atoms are unimpeded between said source of metal atoms and the sensitive material and have access to the entire surface of the sensitive material on the web which forms the sides of said development chamber.
 6. The image exposure and development apparatus of claim 5 further including protection means for protecting a zone from said source of metal atoms so that, as said rotatable discs rotate past said zone, the portion of said discs facing said zone are protected from deposition of metal atoms.
 7. The image exposure and development apparatus of claim 4 wherein said discs have a concentration of developer atoms on their surfaces below 1014 atoms/cm2.
 8. The image exposure and development apparatus of claim 7 wherein said web is fed from said exposure means and is positioned around said rotatable discs and carries a latent image thereon, the latent image receiving a surface concentration of atoms of developer material in excess of 1014 atoms/cm2.
 9. The image exposure and development apparatus of claim 8 wherein a wiper means is positioned against said discs so that metal atoms deposited upon said discs are removed by said wiper means as said discs rotate. 